The present invention relates to a method and apparatus for rotating dots of data so as to easily edit and/or display rotated dots of data with a small circuit.
In the prior art, for example, in Japanese Patent Laid-open No. 59-60490 (1984) there is disclosed an apparatus in which there is an n.times.n dot matrix memory and a plurality of selectors for rotating outputs of the memory by 90.degree., 180.degree., 270.degree., etc., and an input direction of n dots of parallel data into the memory is limited to only one direction, that is, a to row direction or a column direction.
In this prior art, in order to rotate n.times.n dots of data, it is necessary to write n dots of parallel data n times into the memory, and to read n dots of parallel data n times from the memory. Namely, assuming that the n dots of parallel data make up one word, and the input and output operation of one word of data constitutes one cycle, 2n cycles are needed for rotating n words of image data. Since it is generally necessary to execute operations of n words of data by n cycles for processing image data in real time, it is impossible to process them in real time in this prior art.
Further, in variations of the above prior art, it is well known as a double-buffer method that a pair of matrix memories can be prepared, and a store to one memory and a read out from another memory can be simultaneously executed in the real time. However, in this double-buffer method, it is essentially necessary to use two n.sup.2 bit memories, so that the circuit configuration becomes larger.